<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type = "text/javascript">
        var i;
        alert(i);
        i = 12;
        alert(typeof(i));
        i = "abc";
        alert(typeof(i));
        var a = "abc";
        alert(a*i);
        b = "12";
        alert(b);
    </script>
</head>
<body>

</body>
</html>